The formation of fine patterns has been desired for semiconductor devices such as a semiconductor integrated circuit (LIS: Large Scale Integration) along with the improvements in the integration degree, and the minimum pattern has been currently reached the size of 100 nm or smaller.
The formation of such fine patterns in a semiconductor device is realized by an exposure technique using an electron beam capable of forming a fine pattern in the size of 100 nm or smaller. However, the exposure technique using this electron beam has problems such that the through-put thereof is low and it is not suitable for a low-cost mass-production. Therefore, it has been attempted to shorten the wavelength of a light source of an exposure device in the exposure technique without using an electron beam (e.g., an EUV (extreme ultraviolet) exposure using a soft X-ray having a wavelength of 13.5 nm as a light source). However, to shorten the wavelength of the light source of the exposure device, it is necessary to update the exposure device, and thus a significant amount of the cost is expected for the updating. Moreover, to form a fine pattern, an improvement of a resist material is also desired so as to have high resolution corresponded to the properties of the light source of the exposure device. However, the improvement of the resist material has a limitation, and it is extremely difficult to satisfy all the required properties for the resist material. Accordingly, there has been desired to provide a technique capable of accurately forming a uniform and fine resist pattern without updating the exposure device or improving the resist material.
As a method for forming a fine resist pattern, by which the formation of a fine pattern that extends the exposure limit (the resolution limit) of an exposure light source by means of the conventional exposure device, there has been a method that uses a resist pattern thickening material (may also be referred as “a resist swelling agent”) configured to thicken a resist pattern so as to be able to form a fine reverse pattern (the space formed between the adjacent resist patterns) from the resulted resist pattern. For example, there has been known a technique (RELACS) for forming a desired fine pattern (e.g., a wiring pattern) having the same shape as a reverse pattern from a resist pattern (see Japanese Patent Application Laid-Open (JP-A) No. 10-73927). In this technique, after forming a KrF resist pattern by exposing a KrF resist film to KrF (krypton fluoride) excimer laser light (a wavelength of 248 nm) that is a deep UV ray, a coating film is formed so as to over the KrF resist pattern, the coating film and the KrF resist pattern are allowed to interact to each other at the contact interface by using a residual acid contained in the KrF resist pattern so as to thicken (swell) the KrF resist pattern to thereby shorten a pitch of the KrF resist pattern. As a result, a fine reverse pattern of the KrF resist pattern is formed.
However, the resist pattern thickening material used for RELACS has a problem such that it does not work on an ArF resist pattern formed by exposing an ArF resist film to ArF (argon fluoride) excimer laser light (a wavelength of 193 nm) that is currently used for a fine processing technique. Moreover, as the resist pattern thickening material thickens a resist pattern by a crosslinking reaction induced by a crosslinking agent contained in the resist pattern thickening material and the residual acid generated in the resist pattern, the thickened amount of the resist pattern varies depending on the size of the original resist pattern before being thickened, and it is very sensitive to the changes in the processing temperature for a wafer. Accordingly, it is difficult to apply such the resist pattern thickening material in the practical use.
As a technique to solve the aforementioned problem, there has been known a technique for forming a fine pattern by using a non-crosslink resist pattern thickening material containing, as an essential substance, a water-soluble aromatic compound such as benzyl alcohol, benzyl amine and derivatives thereof (see JP-A Nos. 2006-259692 and 2007-148272). By using this resist pattern thickening material, it becomes easy to control a reaction as no crosslinking reaction occurs, a resist pattern is thickened without depending on a size of the resist pattern, and it has large tolerance (margin) for the changes in the processing temperature for a wafer. Accordingly, this resist pattern thickening material has been applicable in the practical use.
However, in the case where the processing temperature for a wafer is set high, it has been found out that the water-soluble aromatic compound contained in the non-crosslink resist pattern thickening material is sublimated if a boiling temperature of the water-soluble aromatic compound is lower than the processing temperature. It has been concerned that the sublimated water-soluble aromatic compound be precipitated on an inner wall of a chamber including a hot plate, which is a heating unit, or in an exhaust pipe, then re-deposited on the wafer that is a subject to be processed.
For a material for forming a semiconductor in the form of a coating solution, the defects caused by the re-deposition of sublimates are problems in the production, such as lowing yields or lowing performance of a final product (see, for example, JP-A Nos. 2005-165096 and 2007-114245). Therefore, it is also necessary to avoid the risk for the substances contained in the resist pattern thickening material to be sublimated and re-deposited on a wafer.